1. Field of the Invention
This invention relates to a write protect switch device for use with computers, word processors and the like, which is accommodated in a disk drive for performing recording and reproducing of information with respect to a magnetic disk encased in a casing and detects whether the magnetic disk is write-enabled or -disabled.
2. Description of the Prior Art
In systems of performing recording and reproducing of information with respect to a disk cartridge having a magnetic disk encased in its casing by means of a disk drive, various status detecting sensors and switches for checking the conditions of the disk and disk drive are equipped, such as an index sensor, write protect switch, track 00 switch, disk detecting switch, and door switch. Among them, the write protect switch is used to detect the presence/absence of a write protect notch formed in an outer marginal portion of the casing which indicates whether the disk may be written on. The write protect switch sets the system in a state wherein it can write information onto the disk only when the notch has been detected, whereby dissipation or destruction of recorded data is prevented from occurring.
FIG. 9 is a plan view of a 51/4 in. disk cartridge, this disk cartridge 10 comprises a flexible casing 10a and a flexible magnetic disk 10c encased in the former, and at given spots of the casing 10a are formed a spindle bore 10b, head insertion window 10e, index hole 10f, and write protect notch 10g. The write protect notch 10g is formed by cutting off a portion of given size at a given point from one margin on the side opposite to the side where the head insertion window 10e is formed. The system is designed so that as the disk cartridge 10 is inserted in the disk drive with the side of its head insertion window 10e headed and when the disk cartridge 10 arrives at a given load position (clamp position), a photosensor or a mechanical write protect switch composed of a micro switch located at the position of the write protect notch can detect the presence/absence of that notch 10g.
The write protect switch is generally made up by the use of, for example, a photosensor, reed switch, or micro switch, and in many cases, made up of the photosensor capable of detecting the notch 10g without need of contact. However, the write protect switch composed of the photosensor had the problem that it can hardly answer to a demand for cost reduction because the photosensor is high in part cost and large in power consumption.
Among mechanical switches which seemed to realize cost reduction, one write protect switch of the above kind used in the prior art is shown in FIG. 10, which comprises a micro switch 47 and a lever 60 swingable in response to the presence/absence of the write protect notch 10g. This lever 60 is made by an elastic member into the form of a single unit and urged elastically in the counterclockwise direction in the drawing about its base end portion 60a, a slide 47a of the micro switch 47 abuts on the back face (the under face in the drawing) of the lever 60, and in response to the swing of the lever 60 the switching action can be brought about. Specifically, while the disk cartridge 10 is being inserted and ejected an abutting portion 60b of the lever 60 slides on one side surface of the casing 10a thereby causing the lever 60 to locate at position A indicated by the one-dot chain line. During the above, the slide 47a is pushed into the body of the micro switch 47 to disable the disk from being written. When the disk cartridge 10 is inserted up to a given position and arrives at the clamp position, the write protect notch 10g moves to a position opposite to the abutting portion 60b of the lever 60, and if the portion of the notch 10g is vacant, the abutting portion 60b fits into the notch 10g and the lever 60 turns in the counterclockwise direction in the drawing. As a result, the slide 47a of the micro switch 47 projects, so that a signal indicating that the disk is writable is generated. Thus, writing onto the disk is enabled. On the contrary, if the abutting portion 60b cannot fit into the notch 10g and the micro switch 47 cannot be actuated when the abutting portion 60b of the lever 60 has arrived at the position of the notch 10g, writing is disabled even when the disk cartridge 10 has been loaded up to a given position. If it is desired to bring about this write-disabled state, a foil member B, for example, is bonded to the position of the notch 10g as indicated by the one-dot chain line in FIG. 9 to prevent the abutting portion 60b from fitting into the notch 10g. The Foil member B intercepts the path of light to disable writing on the disk.
According to the conventional mechanical write protect switch device configured as above, the depth of the write protect notch 10g was made to accord with the thickness of the casing 10a, so that the swing stroke of the lever 60 was very small and the stroke of the slide 47a reciprocated by the former was also small; thus, it was required to adjust the micro switch 47 very accurately. Consequently, to achieve accurate adjustment a very-long time was needed for adjustment at the time of assembly and/or after assembly, resulting in an increase in assembly cost. Further, to make the mechanism operate by a minute stroke while the abutting portion 60b is urged in the counterclockwise direction in the drawing by means of the slide 47a of micro switch 47 and the elasticity of the lever 60, the elastic portion (base end portion 60a) of the lever 60 was made comparatively rigid; thus, there resulted in a problem relating to the reliability of operation. In addition, there was a fear that the casing 10a would be pushed and deformed by the foregoing urging force when the abutting portion 60b slides on the casing 10a, and another fear was also that if some deformation appears the rotational characteristic of the disk would be degraded.